Nuclear reactor installation

Claim 1

A NUCLEAR REACTOR INSTALLATION COMPRISING A SHIELD STRUCTURE DEFINING AN INTERNAL PRESSURE ENCLOSURE; A REACTOR CORE IN THE ENCLOSURE; A HEAT EXCHANGE ASSEMBLY IN THE ENCLOSURE SPACED FROM THE CORE AND COMPRISING A PLURALITY OF ELEMENTARY UNITS EACH COMPRISING A SET OF HEAT EXCHANGE TUBES; MEANS FOR CIRCULATING A GASEOUS PRIMARY COOLING FLUID THROUGH THE CORE AND PAST THE HEAT EXCHANGE TUBE; MEANS FOR CIRCULATING A SECONDARY COOLING FLUID THROGH THE HEAT EXCHANGE TUBES; MEANS PROVIDING A FLOW CIRCUIT FOR THE SECONDARY FLUID EXTERNALLY OF THE SHIELD STRUCTURE; A SERVICING CHAMBER IN THE ENCLOSURE SPACED FROM THE CORE AND FROM THE HEAT EXCHANGE ASSEMBLY; WALL MEANS SHIELDING SAID CHAMBER FROM THE CORE AND HEAT EXCHANGE ASSEMBLY IN RESPECT TO RADIATIONS; PASSAGE MEANS THROUGH THE SHIELD STURCTURE PROVIDING ACCESS TO THE SERVICING CHAMBER; AND FLOW MEANS CONNECTING THE HEAT EXCHANGE TUBES TO SAID EXTERNAL CIRCUIT SAID CONNECTING MEANS INCLUDING INLET AND OUTLET CONDUIT MEANS ASSOCIATED WITH EACH OF SAID UNITS AND EXTENDING FROM SAID EXTERNAL CIRCUIT MEANS THROUGH THE SHIELD STRUCTURE INTO THE SERVINING CHAMBER, PIPES CONNECTED TO INLET ENDS OF THE RESPECTIVE TUBES IN EACH UNIT AND EXTENDING INTO SAID SERVICING CHAMBER FOR CONNECTION THEREIN WITH THE INLET CONDUIT MEANS ASSOCIATED WITH THAT UNIT, AND PIPES CONNECTED TO OUTLET ENDS OF THE RESPECTIVE TUBES OF EACH UNIT AND EXTENDING INTO THE SERVICING CHAMBER FOR CONNECTION THEREIN WITH THE OUTLET CONDUIT MEANS ASSOCIATED WITH THAT UNIT; AND CUT-OFF VALVE MEANS ASSOCIATED WITH SAID CONDUIT MEANS AND OPERABLE FROM OUTSIDE THE SHIELD STRUCTURE TO ISOLATE ANY ONE OF SAID UNITS.